This invention relates to improvements in gearings in general, and more particularly to improvements in gearings of the type wherein an internal gear surrounds a second gear having an annulus of external gear teeth in mesh with the annulus of gear teeth forming part of the internal gear. Gearings of the type to which the present invention pertains are often utilized in pumps, e.g., in so-called internal gear pumps which serve to supply a lubricant (such as oil) to various constituents of the power train in a motor vehicle.
Published German patent application Serial No. 199 23 851 discloses a gearing wherein a housing confines a rotary internal gear mating with a pinion which is installed within the internal gear and defines therewith a relatively large crescent-shaped chamber. The pinion receives torque from a prime mover (e.g., from the engine of a motor vehicle) by way of a shaft, such as a transmission shaft, and causes the internal gear to rotate about an axis which is parallel to the rotational axis of the pinion. One end of the crescent-shaped chamber communicates with an inlet (e.g., a port provided in the housing) for admission of a hydraulic fluid, and the other end of such chamber communicates with an outlet provided in the housing to receive a flow or stream of fluid which is pressurized on its way through the chamber.
A drawback of many presently known gearings of the above outlined character is that the flow of fluid through the crescent-shaped chamber is rather turbulent with attendant undesirable effect upon the characteristics of the body of fluid (such as lubricant) which is being conveyed into and beyond the outlet of the housing. For example, eddy currents developing in the body of liquid flowing through the crescent-shaped chamber can cause an overheating of a modern internal gear pump with attendant problems involving adequate cooling of the pressurized fluid and/or of the mechanical parts of the power train in a motor vehicle.
Internal gear pumps of the above outlined character are described and illustrated, for example, on pages 492-493 of xe2x80x9cModern Automotive Technologyxe2x80x9d authored by James E. Duffy and published in 1994 by The Goodheart-Willcox Company, Inc., Tinley Park, Ill. The gear pump which is described in this publication comprises an oil pump body or housing which confines a driven (internal) gear and a drive gear (pinion) which mates with the driven gear and receives torque from a so-called drive spline. The latter can receive torque from or can form part of the distributor, the crankshaft or an accessory shaft and mates with a driven spline in the drive gear. Lubricant (oil) at the inlet side of the pump is caught in the gear teeth and is carried around the outer wall inside the pump housing. When the lubricant reaches the outlet side of the pump, the gear teeth mesh and seal. Lubricant caught in each gear tooth is forced into the pocket at the pump outlet and pressure is formed. This causes the lubricant to squirt out of the pump and to the engine bearings and/or to other component parts which necessitate reliable, thorough, frequent or continuous lubrication. Such principle underlies the operation of a gear oil pump as well as that of an internal gear oil pump.
As utilized in this specification and in the appended claims, the term xe2x80x9cspur gearxe2x80x9d is intended to denote a gear (such as a pinion) having an annulus of external teeth regardless of the exact configuration and/or orientation of the teeth (i.e., (helical) teeth set obliquely to the axis of rotation, radial teeth parallel to the axis of the wheel, or others).
Commonly owned U.S. Pat. No. 5,667,448 (granted Sep. 16, 1997 to Oswald Friedmann for xe2x80x9cPOWER TRAINxe2x80x9d) discloses certain features of a power train which can employ an internal gear pump for a suitable lubricant, such as oil.
An object of the present invention is to provide a novel and improved gearing of the type wherein a housing confines an internal gear and a spur gear mating with the internal gear.
Another object of the invention is to provide a novel and improved internal gear pump which can be utilized with advantage in the power trains of motor vehicles.
A further object of the instant invention is to provide a novel and improved method of influencing the flow of a hydraulic fluid (such as oil) through the crescent-shaped chamber of an internal gear pump.
An additional object of the invention is to provide a novel and improved method of enhancing the performance of an internal gear pump which can be utilized with advantage in the lubricating systems of power trains in motor vehicles.
Still another object of the invention is to provide a gearing of the type wherein an internal gear and a spur gear mate in a housing and define a crescent-shaped chamber, particularly for compression of a hydraulic fluid entering at one end of the chamber and exiting at the other end.
A further object of the invention is to provide novel and improved means for preventing or greatly reducing turbulence in the sickle-shaped chamber between an internal gear and a spur gear in the housing of an internal gear pump, especially for use in the power trains of motor vehicles.
Another object of the invention is to provide novel and improved inserts for use in the sickle-shaped chambers of gearings employing mating internal gears and spur gears.
An additional object of the invention is to provide a gearing which constitutes an improvement over and a further development of gearings disclosed in the aforementioned published German patent application Serial No. 199 23 851 as well as in published German patent applications Serial Nos. 37 23 557 A1 and 43 22 239 A1.
Still another object of the invention is to provide an internal gear pump which constitutes an improvement over and a further development of pumps of the type disclosed in the aforementioned published German patent applications.
One feature of the present invention resides in the provision of a gearing which comprises a housing, an internal gear which is rotatably mounted in the housing, and a spur gear which is rotatably mounted in the housing, which mates with the internal gear and which defines with the internal gear a substantially crescent-shaped chamber. The improved gearing further comprises an engine- or motor-driven shaft or other suitable means for rotating one of the gears to thus rotate the other gear, and an insert which is provided in and at least substantially fills the chamber. The insert includes a first filler, at least one abutment for the first filler, and a second filler.
The at least one abutment is or can be disposed between the first and second fillers, as seen in the circumferential direction of the internal gear.
At least one of the fillers has or can have an outline resembling a portion of the outline of the substantially crescent-shaped chamber. Such at least one filler can occupy approximately one-half of the chamber. For example, each of the fillers can have an outline resembling that of a portion of the substantially crescent-shaped chamber, and each filler can occupy approximately one-half of the chamber.
At least one of the fillers can comprise a plurality of (e.g., two) discrete sections. The arrangement can be such that the insert comprises only two fillers, that one of the fillers is a one-piece component, and that the other filler comprises a plurality of sections.
The housing can be provided with a fluid-admitting inlet which communicates with one end portion of the chamber and with a fluid-evacuating outlet which communicates with the other end portion of the chamber. The two end portions of the chamber are spaced apart from each other as seen in the circumferential direction of the internal gear. One of the fillers of the insert can be installed in the chamber adjacent the inlet, and the other filler of the insert can be installed in the chamber adjacent the outlet. The at least one abutment is or can be rigid with the housing and can be disposed intermediate the one filler and the other filler, as seen in the circumferential direction of the internal gear.
The housing can form part of an internal gear pump.
In many or most instances, the engine- or motor driven gear is the spur gear.
One of the fillers can comprise discrete first and second sections and at least one sealing element between the first and second sections.
The means for rotating the one gear can comprise a power-driven drive spline and a complementary internal spline provided in the spur gear and meshing with the drive spline.
Certain teeth of the internal gear mate with the adjacent teeth of the spur gear in a region which is adjacent the inlet and/or the outlet of the chamber, for example, in a region located between the inlet and the outlet and opposite the chamber.
Another feature of the invention resides in the provision of a gearing which comprises a housing, an internal gear which is rotatably mounted in the housing, and a spur gear which is rotatably mounted in the housing, which mates with the internal gear and which defines with the internal gear a substantially crescent-shaped chamber. The improved gearing further comprises means for rotating one of the gears to thus rotate the other gear by way of the one gear, and a substantially crescent-shaped insert which is provided in and at least substatially fills the chamber. The insert or the housing has an elongated groove, and the housing or the insert has a follower which extends into the groove.
The groove can be provided in the insert and the follower then includes a first portion which is rigid with or is rotatably or turnably mounted in the housing and a second portion which extends into the groove.
The chamber has first and second end portions which are spaced apart from each other as seen in the circumferential direction of the internal gear, and the housing is or can be provided with an inlet in communication with one end portion and an outlet in communication with the other end portion of the chamber.
The insert can comprise at least two discrete fillers.